Such welding electrode units are known, for example, from industrial production systems, in which work pieces are welded at high cycle speeds. In this regard, the welding electrodes perform forward movements, in order to enter into contact with a work piece to be welded. In this regard, it is absolutely necessary that the welding electrode unit contacts the work piece with a welding electrode, in order to maintain the electrical current required for the welding process. If contact is interrupted, the flow of current through the welding electrode stops, whereupon the welding process stops. Such a break in contact between welding electrode and work piece often takes place necessarily if the welding process melts part of the work piece, at least for a certain period of time. The interrupted welding process then has a disadvantageous effect on the strength and the visual point quality (surface quality) of the weld.
In order to guarantee a continuous welding process, apparatuses are known in the state of the art, such as, for example, the ones from the document DE 10 2010 005 357 A1, which ensure a repositioning movement and prevent interruption of contact. The success of the apparatus from the document DE 10 2010 005 357 A1 is due, among other things, to the fact that the pressure of the welding electrode on the work piece can be kept essentially constant. For this purpose, it is necessary that a repositioning device is held in position, in the welding position, by way of an energy source. In this regard, the movement of the welding electrode is determined by coupling the repositioning movement with the forward movement.